WO2009141097A1

WO2009141097A1 - A vane with tilting tips, and a rotary displacement pump using this vane

Info

Publication number: WO2009141097A1
Application number: PCT/EP2009/003460
Authority: WO
Inventors: Franco Fermini; Vittorio Polloni
Original assignee: Vhit S.P.A. Unipersonale
Priority date: 2008-05-22
Filing date: 2009-05-12
Publication date: 2009-11-26
Also published as: ITTO20080382A1; EP2304182A1; CN102037218A

Abstract

A vane for a displacement pump comprising a body (1), a profiled pumping chamber (2) defined within said body (1), and a rotor (4) rotatably mounted within said body (1), eccentric with respect to the pumping chamber (2) and carrying a vane (5) whose end portions slide against the inner surface (3) of the pumping chamber (2), characterized in that each operating end portion of the vane (5) is formed by a tilting tip (9) having a coupling means (11) articulated with respect to the vane body (5) and suitable for tilting within a limited field with respect to the vane body (5), the shape of the tip (9) and the allowed tilting field being such that the tilting tip (9) is applied against the inner surface (3) of the pumping chamber (2) when the vane (5) is rotated in a preestablished working direction (F1), and being such that the tip (9) is allowed to retract from the inner surface (3) of the pumping chamber (2) when the vane (5) is rotated in the direction (F2) opposite to the preestablished operating direction (F1). The invention also concerns a rotary displacement pump comprising at least a vane with tilting tips.

Description

DESCRIPTION

A VANE WITH TILTING TIPS, AND A ROTARY DISPLACEMENT PUMP

USING THIS VANE

BACKGROUND OF THE INVENTION The subjects of this invention are a vane with tilting tips and a rotary displacement (volumetric) pump using this vane.

In the rotary displacement pumps having a pumping chamber and a rotor with a single vane, mounted in the pumping chamber and rotatable around a rotation axis eccentric with respect to the axis of the pumping chamber, the end portions of the vane should sealingly slide against the wall of the pumping chamber, and this requires that the pumping chamber has a special shape which is defined by all the diameters of the chamber passing through the rotation axis of the rotor being identical to each other; this shape is currently, even if not properly, defined as elliptical. Despite a precise and expensive manufacture, the attainment of a suitable sealing requires that use is made of yielding packings mounted at the ends of the vane. These packings cause a undesirable friction increase and in the long run, after having suffered a wear, they cause an increase of the clearances and a reduction of the pump duration. The proper sealing and the regular sliding of the vane against the surface of the pumping chamber are heavily disturbed by impurities that may possibly be present.

The obtained sealing is independent from the rotation direction of the pump, whereby, if by accident the pump is rotated in the direction opposite the preestablished working direction, some overload can arise which are ca- pable of damaging the pump itself or the driving mechanisms thereof. Such rotations in the opposite direction take place in various circumstances in the displacement pumps, in particular in the vacuum pumps installed on automotive vehicles, which are driven by the vehicle engine that on its turn is subjected, in special circumstances, to suffer counterrotations. Another drawback of the pumps in question resides in a certain noise and vibration, which is due to the vane sliding against the surfaces of the pumping chamber under a relatively high pressure.

The stated drawbacks or similar disadvantages are also verified in displacement pumps of a kind different from the pumps with a single vane. SUMMARY OF THE INVENTION

The main object of this invention is therefore to provide a vane, as well as a rotary displacement pump using this vane, which should be capable of reducing in an important measure the stated drawbacks which are verified in the known displacement pumps.

A special object of the invention is to systematically preserve both the pump itself and the driving means thereof against overloads generated by a possible counterrotation.

Another object of the invention is to allow a less critical manufacture of the pumping chamber that requires a special shape.

Still another particular object of the invention is to reduce the friction of the vane against the surface of the pumping chamber, and therefore to reduce the consumed energy, the produced heating, the vibrations and the noise. Still another object of the invention is to reduce the sensitivity of the pump to possible impurities present within the pumping chamber.

The subject of this invention is a vane for a rotary displacement pump comprising a body, a profiled pumping chamber defined within said body, and a rotor rotatably mounted within said body, eccentric with respect to the pumping chamber and carrying a vane whose end portions slide against the surface of the pumping chamber, characterized in that each operating end portion of the vane is formed by a tilting tip, having a coupling means articulated with respect to the vane body and suitable for tilting within a limited field with respect to the vane body, the shape of the tip and the allowed tilting field being such that the tip is applied against the surface of the pumping chamber when the vane is rotated in a preestablished working direction, and being such that the tip is allowed to retract from the surface of the pumping chamber when the vane is rotated in the direction opposite to the preestablished operating direction. Preferably, to each tilting tip articulated to the vane body is also allowed a limited displacement along the longitudinal direction of the vane.

As a consequence, when the pump is rotated in the preestablished working direction, the vane tilting tips take a position of contact against the surface of the pumping chamber, thus suppressing the existing clearance even if the profile of the pumping chamber does not exactly correspond to the right profile, and even if the tips have suffered a certain wear.- Therefore, the pumping chamber can be worked with a reduced precision in a less expensive way; its profile can be brought near to a circular profile thus making easier the manufacture, simplifying the geometry and the maintenance of the production equipments and resulting in a more regular displacement. Possible present impurities can be overridden thanks to a momentary yielding and oscillation of the tilting tips, without troubles. It is not required to foresee any increased pressure of the vane against the surface of the pumping chamber in order to ensure the sealing, and this reduces the friction, the consumed energy and the produced heating, and increases the reliability and the duration of the pump. The suppression of the clearance and the adaptability in position of the tilting tips reduces the noise and vibration of the pump.

On the other hand, when by accident the pump is rotated in the di- rection opposite to the preestablished working direction, the tilting tips are allowed to oscillate in such a manner as to retract from the surface of the pumping chamber. Then ceases the sealing of the vane with respect to the pumping chamber and no overpressure or reverse pressure can arise that could give rise to abnormal stresses and damage the pump itself or the driv- ing means thereof. The sure suppression of the overloads also allows adopting in the manufacture of the component parts some materials having less valuable technical characteristics and, therefore, less expensive.

Preferably, each tilting tip has in its section a head portion intended to cooperate with the inner surface of the pumping chamber, and this head portion is connected by a neck portion to a substantially cylindrical portion intended to form a means for coupling the tip with the vane body.

Preferably, said head portion of the tilting tip is asymmetrical. It is of advantage that each end portion of the vane has a seat which is intended to house the coupling means of the tip, and has a pair of surfaces directed from this seat to the vane end and arranged for limiting the oscillation field allowed to the tilting tip.

Preferably, said seat intended to house the coupling means of the tip is somewhat elongated along the longitudinal direction of the vane, and it allows a limited displacement of the coupling means of the tip along the longi- tudinal direction of the vane. The pump according to the invention, provided with tilting tips, is mainly suitable for the automotive application as a vacuum pump, intended to supply a pneumatic servomotor for braking assistance or other apparatuses or pneumatic actuators which require a depression. However the features according to the invention are also suitable for application in displacement pumps of other kinds or intended for different functions.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other characteristics, objects and advantages of the subject of the present invention will more clearly appear from the following de- scription of an embodiment being a non limiting example, with reference to the accompanying drawings, wherein:

Figure 1 shows a cross section of a pump according to the invention, seen in the condition of rotation in the preestablished working direction.

Figure 2 shows a similar section, but the pump being seen in the condition of rotation in the direction opposite to the preestablished working direction.

Figure 3 shown on a larger scale a cross section of an end vane portion with the corresponding tilting tip, in the condition of rotation of the pump in the preestablished working direction. Figure 4 shows a section corresponding to that of Figure 3, but in the condition of rotation of the pump in the direction opposite to the preestablished working direction.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The shown and described pump comprises a body 1 wherein there is defined a pumping chamber 2, whose inner surface 3 is intended to cooperate with the end portions of a vane. A rotor 4 is installed within the body 1 and it is rotatable around an axis O eccentric with respect to the axis C of the pumping chamber 2. The pumping chamber 2 has a special shape which is defined by all the diameters of the pumping chamber passing through the ro- tation axis 0 of rotor 4 being identical to each other. However, for the already stated reasons, when applying the invention this conformation may be somewhat modified, approximated or simplified with respect to the theoretical geometry. As it is customary, the pumping chamber 2 has two openings (not represented), respectively a suction opening and a delivery opening, which are suitably disposed with respect to rotor 4.

In rotor 4 there is installed a vane, whose flat body 5 can sealingly slide along its own longitudinal direction within rotor 4. According to the essential characteristic of the invention, each end portion of the vane body 5 does not cooperate, directly or through a yielding packing, with the inner surface 3 of the pumping chamber, as it is usual according to the known technique, but to this aim it carries a tilting tip 9 susceptible of oscillating. Each tilting tip 9 has, in its section, a head portion 10, a substantially cylindrical portion 11 and a neck portion 12 which mutually connects the head portion 10 and the cylindrical portion 11. The head portion 10 is the portion of the tilting tip that is intended to cooperate by sliding against the inner surface 3 of the pumping chamber 2. In view of the behavior of the head portion 10 with respect to the inner surface 3 of the pumping chamber 2 being different according to the rotation direction of the pump, as it has already been stated and it will be explicated in more detail later on, it may be of advantage that the head portion 10 be asymmetrical, as it has been represented. On its turn, the vane body 5 has at each longitudinal end portion a seat 6 housing the cylindrical portion 11 of tip 9. It is preferable that, as it appears from Figures 3 and 4, said seat 6 is somewhat elongated in the vane longitudinal direction, rather than being of circular cross section, whereby the cylindrical portion 11 of tip 9 enjoys within seat 6 of a limited freedom of movement along the longitudinal direction of the vane, and it can displace along a limited stretch outwards (as shown in Figure 3) or inwards (as shown in Figure 4).

From seat 6 extend towards the vane end two surfaces 7 and 8, and between said two surfaces is arranged the neck portion 12 of tip 9. These surfaces, by cooperating with the neck portion 12, allow a limited oscillation of tip 9 in the counterclockwise direction (as shown by Figure 3) or in the clockwise direction (as shown in Figure 4).

The whole of the described conformations of the tilting tip 9 and of the end portion of the vane body 5 allows realizing the two conditions repre- sented respectively in Figures 3 and 4. The presence in a displacement pump of a vane having tilting tips defines a displacement pump also being a subject of this invention.

The operation of the described vane and pump is as follows. The following description is done with reference to only one tip 9, because it is obvious that the description can be applied identically to the opposite tip 9.

We suppose that the preestablished working direction of the pump is the clockwise direction. When the pump rotor 4 is rotated in the clockwise direction according to arrow F1 of Figure 1 , tip 9 aims to stay behind with respect to the vane body 5: it takes the position represented in Figure 3, and it is applied against the inner surface 3 of the pumping chamber 2, thus exerting its sealing action against the same and allowing a normal operation of the pump. Both the pressure generated by the pump and the action of the lubricating oil present act in the same way in maintaining the tip 9 in the working position represented in Figure 3. However during this operation, when it is needed, the tilting tip can carry out small oscillations or translations, both in order to exactly follow the profile of surface 3 (even if this profile does not exactly correspond to the theoretically correct profile), and in order to override small obstacles formed by possible impurities present. If on the contrary, for any reason, the pump is rotated in the counterclockwise direction according to arrow F2 of Figure 2, namely, in the direction opposite to the preestablished working direction F1 , tip 9 aims to stay behind with respect to the vane body 5: it oscillates by taking the position represented in Figure 4. In this position, tip 9 is separated from the inner surface 3 of the pumping chamber 2, and therefore it does not exert any sealing action. As a consequence the pump idles and it cannot generate any noticeable pressure. In any event, both the very small pressure still generated and the action of the lubricating oil act in the same way in maintaining the tip 9 in the not working position represented in Figure 4. Accordingly, when the pump suffers a counterrotation it idles without opposing a noticeable resistance, whereby there is prevented any overload susceptible of damaging the vane or any other member of the pump or of the driving system thereof.

It follows the achieving of the already stated advantages regarding the protection against overloads, the possibility of simplifying the profile of the pumping chamber, an increased efficiency and duration of the pump, the possibility of using less valuable materials, and also a reduction of the pump noise, the energy consumption and the heating.

This invention is not limited to the embodiment described and shown as an example. The described and shown details cannot be considered as limiting the invention. In particular, the shape of the tilting tip and the seat supporting the same can be chosen in various manners according to the need of any specific application. Moreover, the application of the idea of the invention is not limited to the pumps with a single vane or to the vacuum pumps, but it can be extended to several types of displacement pumps and to several application fields thereof.

Several possible modifications have been stated in the course of the description, and others are within the capacity of the technicians skilled in the art. These and other modifications can be made in what has been described and shown, without departing from the spirit of the invention and the scope of this Patent as defined by the appended Claims.

Claims

1 . A vane for a rotary displacement pump comprising a body (1 ), a profiled pumping chamber (2) defined within said body (1), and a rotor (4) rotatably mounted within said body (1 ), eccentric with respect to the pumping chamber (2) and carrying at least a vane (5) whose end portions slide against the inner surface (3) of the pumping chamber (2), characterized in that each operating end portion of the vane (5) is formed by a tilting tip (9) having a coupling means (1 1 ) articulated with respect to the vane body (5) and suitable for tilting within a limited field with respect to the vane body (5), the shape of the tip (9) and the allowed tilting field being such that the tilting tip (9) is applied against the inner surface (3) of the pumping chamber (2) when the vane is rotated in a preestablished working direction (F1 ), and being such that the tilting tip (9) is allowed to retract from the inner surface (3) of the pumping chamber (2) when the vane (5) is rotated in the direction (F2) oppo- site to the preestablished operating direction (F1 ).

2 . A vane for a displacement pump, as set forth in Claim 1 , characterized in that to each tilting tip (9) articulated to the vane body (5) is also allowed a limited displacement along the longitudinal direction of the vane (5).

3 . A vane for a displacement pump, as set forth in Claim 1 , charac- terized in that each tilting tip (9) has in its section a head portion (10) intended to cooperate with the inner surface (3) of the pumping chamber (2), this head portion (10) being connected by a neck portion (12) to a substantially cylindrical portion (1 1 ) intended to form a means for coupling the tip (9) with the vane body (5).

4 . A vane for a displacement pump, as set forth in Claim 3, characterized in that said head portion (10) of the tilting tip (9) is asymmetrical.

5 . A vane for a displacement pump, as set forth in Claim 1 , characterized in that each end portion of the vane (5) has a seat (6) which is intended to house the coupling means (1 1 ) of the tilting tip (9), and it has a pair of surfaces (7,8) directed from this seat (6) to the vane end and arranged for limiting the oscillation field allowed to the tilting tip (9).

6 . A vane for a displacement pump, as set forth in Claim 1 , characterized in that said seat (6) intended to house the coupling means (11 ) of the tilting tip (9) is somewhat elongated along the longitudinal direction of the vane (5), and it allows a limited displacement of the coupling means (1 1 ) of the tilting tip (9) along the longitudinal direction of the vane (5).

7 . A displacement pump, characterized in that it includes at least one vane (5-12) according to one or more of the foregoing Claims.

8 . A displacement pump as set forth in Claim 7, characterized by its automotive application as a vacuum pump, intended to supply a pneumatic servomotor for braking assistance or other apparatuses or pneumatic actuators which require a depression.