Vane for a rotor of a positive displacement vane pump, pump comprising the vane and pumping method using the pump

Abstract

 A vane for a rotary positive displacement pump with a vane rotor has a body (122) in which an inertial damper is mounted. The damper includes at least one inertial dampening member (102) with a mass smaller than the mass of the vane (120) and radially movable within a seat (101) formed in the body, and a pair of resilient members (103a, 103b) opposing the radial movement of the dampening member (102). The invention also concerns a pump using the vane and a pumping method using such a pump.

Description

Technical field

[0001] This invention relates to rotary positive displacement pumps and more specifically it concerns a vane for a pump having a vane rotor.

[0002] The invention also concerns a pump using the vane and a pumping method using such a pump.

[0003] Preferably, but not exclusively, the invention is applied in the so-called single-vane pumps, i.e. pumps where the rotor includes a single vane with constant length, and the following description will mainly refer to this preferred application.

Background of the invention

[0004] Single-vane pumps are often used as vacuum pumps, for instance in the automotive field. They comprise a body defining a chamber with non-circular cross section in which the rotor rotates, in tangential contact, about an eccentric axis. The rotor has a diametrical slot where the vane is mounted and the vane is radially movable in the slot so that, while the rotor is rotating, its ends slide substantially in contact with the internal wall of the chamber. The chamber is divided by the rotor and vane into an intake room and a pressure room, between which a pumped fluid is displaced. An example is disclosed in EP 2 299 055.

[0005] A problem encountered in these pumps is the possible loss of contact between the vane ends and the internal wall of the chamber, in particular at the instants where the radial movement of the vane is reversed (what, as known, occurs twice at each rotor revolution), with a sudden speed change. At those instants, communication can thus be established between the intake and pressure rooms, and this is detrimental to the pump efficiency. Moreover, such a temporary loss of contact also causes a "bounce" of the vane against the wall: this results in a noisy operation and in an early wear of the parts that are designed for being subjected to a mutual sliding friction and, on the contrary, become subjected also to a "pulsating" friction. The problems can become more severe as the vane ends wear.

[0006] Those problems also exist in pumps having a plurality of constant-length vanes angularly distributed on the rotor (which pumps are often used in the automotive field as pumps for the engine lubrication oil) and in pumps with a single variable-length vane, e.g. a vane with tips or contact members distinct from the vane body and capable of a limited radial displacement relative to the body, or a vane comprising two half-vanes radially displaceable relative to each other in their common seat.

[0007] No solution for the above problems is known.

Description of the invention

[0008] It is an obj ect of the present invention to provide a vane for a rotor of a vane pump solving the problems of the prior art.

[0009] According to the invention, this is achieved in that at least one inertial damper or shock-absorber is mounted in said body, said damper including at least one inertial dampening member (hereinafter simply referred to as "dampening member") radially movable within a respective seat, and at least one resilient member opposing the movement of the dampening member.

[0010] In a first embodiment, a single damper is provided and is mounted in an axially central zone of the vane.

[0011] In a second embodiment, a pair of dampers are provided and are mounted in respective seats formed at axially opposite edges of the vane.

[0012] In case of use in a single-vane pump, the or each damper comprises a dampening member kept in a central position by a pair of opposing resilient members engaging the dampening member on the one side and opposite end walls of the respective seat on the other side, or it comprises a pair of dampening members kept agains said walls by an opposing resilient member arranged between the dampening members.

[0013] According to a variant embodiment, each damper includes a single dampening member and a single resilient member, consisting of a leaf spring engaging the ends of the dampening member and the end walls of the seat.

[0014] In case of use in multi-vane pumps, each vane includes, for instance, at least one damper.

[0015] The invention also concerns a vane pump where the or each vane is made in accordance with the invention.

[0016] In a further aspect, the invention also provides a method of pumping by means of a vane pump, comprising the step of inertially dampening the or each vane, at points where the radial sliding direction is reversed, so as to ensure the contact, at said points, between the vane and the internal surface of the pumping chamber, and the inertial dampening is achieved by arranging, inside the or each vane, at least one inertial dampening member radially movable within a respective seat and associated with opposing resilient members arranged to keep the dampening member, in rest conditions, in position in its seat.

Brief Description of the Figures

[0017] The above and other features and advantages of the present invention will become apparent from the following description of preferred embodiments given by way of non limiting example with reference to the accompanying Figures, which show the invention applied to a single-vane pump and in which:

- Fig. 1 shows a conventional single-vane pump;

Fig. 2 shows an alternative vane that can be used in the pump shown in Fig. 1;

Fig. 3 is a cross-sectional axonometric view of a vane according to the invention, in a first embodiment;

Fig. 4 is an exploded axonometric view of the vane shown in fig. 3;

Figs. 5 and 6 are views similar to Figs. 3 and 4, relative to a variant;

- Fig. 7 is an axonometric view of a vane according to the invention, in a second embodiment;

- Figs. 8 and 9 are a cross-sectional axonometric view and a partially exploded axonometric view, respectively, of the vane shown in fig. 7;

- Figs. 10 to 12 are views similar to Figs. 7 and 9, relative to a first variant;

- Figs. 13 and 14 are views similar to Figs. 8 and 9, relative to a second variant; and

- Fig. 15 shows a single-vane pump with an example of a vane according to the invention.

Description of Preferred Embodiments

[0018] The invention will be described in detail in connection with its application in a single-vane pump, as defined above. In order to make understanding of the invention easier, the structure of a conventional single-vane pump will be shortly described. To this end, Figs. 1 and 3 of document EP 2 299 055 are annexed as Figs. 1 and 2, and the same reference numerals have been maintained for the sake of clarity. As said, the present invention is however employable in any pump with vane rotor.

[0019] As shown, pump 10 comprise a housing 40 with fluid inlet and outlet openings 47 and 48, respectively. Housing 40 defines a non-circular pumping chamber 44 having an internal wall 42. Chamber 44 houses a rotor 30 that, in conventional manner, rotates substantially tangent to wall 42, while keeping a small constant clearance. The rotor has a radial slot 26 where a vane 20, radially slidable within the same slot, is mounted. Vane 20 has a body 22 and two tips 24, mounted in body 22 so that they can perform a limited radial movement. The tips slide on wall 42 during rotation of rotor 30, so that the vane and the rotor divide chamber 44 into an intake room 45 and a pressure room 46. Body 20 may have lightening recesses that, depending on their orientation, confer an axial grid structure (recesses 25 in fig. 1) or a radial grid structure (recesses 27 in fig. 2) to the body.

[0020] The vane according to the invention will now be described with reference to Figs. 3 to 14, assuming that it includes a body and two separate tips as in EP 2 299 055. In the Figures relating to the different embodiments of the invention, elements corresponding to those shown in Figs. 1 and 2 are denoted by the same reference numerals, yet preceded by digit 1, 2 etc. Also elements introduced by the invention and having the same or similar functions in the different embodiments are denoted by reference numerals differing by 100 with respect to one another.

[0021] Figs. 3 and 4 show a first exemplary embodiment of the invention, applied to a vane 120 with a radial grid, obtained for instance by means of two pairs of cavities 127 into which teeth 124A of tips 124 are snap fitted. The tips are thus fixed relative to body 122, whereby vane 120 has a constant length.

[0022] A through bore 101, preferably cylindrical, is formed between both pairs of cavities 127, substantially in a central position, and it forms a seat for an inertial shock-absorber or damper 100. "Inertial damper" means a component that, by inertia, tends to oppose the vane movements, in particular to the reversal of the direction of the radial displacement of the vane.

[0023] In this exemplary embodiment, damper 100 includes a dampening member 102, it too cylindrical, arranged to move along bore 101, and a pair or resilient members 103a, 103b, e.g. a pair of coil springs, opposing the movement of dampening member 102 and arranged at both sides of dampening member 102. An end of each spring engages an end portion of dampening member 102, whereas the opposite end abuts against the inner face of tips 124. Springs 103a, 103b have substantially the same length so as to keep dampening member 102, in rest conditions, at a substantially central position.

[0024] Advantageously, dampening member 102 has a smaller mass than vane 120. In any case, its mass depends on the vane mass.

[0025] The material of the dampening member can depend on the material of which the vane body is made, but this is not essential.

[0026] It is clear that the provision of inertial damper 100 confers a greater stability to vane 120, thereby solving the problems mentioned above, since it prevents that any loss of contact between tips 124 and the internal wall of the chamber occurs. Thus, possible bounces and the drawbacks related thereto are avoided. It is also to be noted that the action of damper 100 is favoured by the fluid (air, oil, etc.) present in the chamber where vane 120 moves and penetrating into seat 101.

[0027] In the variant shown in Figs. 5 and 6, damper 200 of vane 220 comprises, in place of a central dampening member opposed by two resilient members, a pair of dampening members 202a, 202b located at the ends of seat 201, so that they rest at one end against tips 224, whereas at the other end they are opposed by the single resilient member 203, still shown as a coil spring, arranged between dampening members 202a, 202b. In this case, it is the overall mass of dampening members 202a, 202b that is smaller than the mass of vane 220.

[0028] It is clear that damper 200 is perfectly equivalent to damper 100.

[0029] Figs. 7 to 9 show a second exemplary embodiment of the invention, applied to a vane 320 with an axial grid comprising two sets of blind cavities 325. In such an embodiment, tips 324 are moulded together with body 322 or moulded onto body 322 and are always fixed relative to the body. Radial seats for a pair of inertial dampers 300', 300" are formed along the opposite axial edges of body 322. Only one seat 301 is clearly visible in the Figures. Cavities 325 open in the bottom of those seats. Each damper 300', 300" is made in similar manner to damper 100 shown in Figs. 3 and 4 and therefore it includes a dampening member 302', 302" (which, in this example, preferably has the shape of a parallelepiped), capable of displacing along seat 301, and a pair of resilient opposing members 303a', 303b' and 303a", 303b", respectively, for instance coil springs. The springs are located at both sides of the respective dampening member 302', 302" and are arranged to keep it, in rest conditions, in a substantially central position in seat 301. The ends of opposing springs 303a', 303b', 303a", 303b" remote from dampening members 302', 302" are kept in position by undercuts or centring members 304', 304" formed e.g. on the internal surface of tips 324 or in the end walls of seats 301, if the latter are shorter than body 322.

[0030] The Figures also show that seats 301 of both dampers 300', 300" communicate at their ends through axial bores 312.

[0031] In the variant shown in Figs. 10 to 12, similarly to the variant shown in Figs. 5 and 6, each damper 400', 400" comprises a pair of dampening members 402a', 402b' and 402a", 402b" having the shape of parallelepipeds, which are located at the ends of respective seats 401 and are opposed by a central spring 403', 403". The dampening members are kept in position by undercuts or centring members 404', 404".

[0032] Figs. 13 and 14 show a further variant of a vane with axial grid. In such a variant, each damper 500', 500" in vane 520 comprises a single dampening member 502', 502", for instance cylindrical, having substantially the same length as the respective seat 501, and an opposing resilient member 503', 503" consisting of a leaf spring, which, for instance, engages cuts 505 in the ends of the respective dampening member 502', 502" and is kept in position by an undercut or a centring member 504', 504" similar to those shown in Figs. 7 to 12.

[0033] Also in all variants of this second embodiment, it is of course the overall mass of the dampening members that is lower than the vane mass.

[0034] For the sake of completeness, Fig. 15 shows, in a view similar to Fig. 1, a pump 110 of the kind shown in Fig. 1 and equipped with the vane according to the invention, in particular and by way of example only vane 120 shown in Figs. 3 to 5. The elements of pump 110 other than vane 120 and the components thereof are still denoted by the same reference numerals as in Fig. 1. Both opposing springs of the dampening member are simply denoted 103.

[0035] It is clear that the above description has been given only by way of non-limiting example and that changes and modifications are possible without departing from the scope of the invention as defined in the following claims.

[0036] More particularly, parallelepiped dampening members can be used in place of the cylindrical dampening members and vice versa. The dampening members could also be prismatic with any cross-sectional shape.

[0037] Moreover, the lightening cavities could be through cavities instead of blind cavities as shown in the drawings.

[0038] Furthermore, in the embodiments shown in Figs. 7 to 12, in case of blind lightening cavities, a single damper located in a central through bore could be used, like in the embodiment shown in Figs. 3 to 6.

[0039] Lastly, even though a vane for a single-vane pump has been shown and discussed in detail, the invention can also be applied to multi-vane pumps, as said before. For instance, in such an application, the vanes could include a single inertial damper in an axially central position, or a pair of dampers at opposite axial edges.

[0040] In accordance with a possible application to multi-vane pumps, the or each damper could include, for instance, a single dampening member and a single opposing member, of which the first is located for instance at the radially internal end of the seat and the second is located for instance at the radially external end of the seat

Claims

1. A vane for a rotor of a rotary positive displacement vane pump, said pump having at least one pumping chamber (44) with an internal wall (42), and said vane (120; 220; 320; 420; 520) having a vane body (122; 222; 322; 422; 522) and two tips (124; 224; 324; 424; 524) and being configured so as to be displaceable in radial direction and to reverse its motion inside said at least one pumping chamber (44), the vane being characterised in that at least one inertial damper (100; 200; 300', 300"; 400', 400"; 500', 500") is mounted in said vane body, said damper including at least one inertial dampening member (102; 202a, 202b; 302', 302"; 402a', 402b', 402a", 402b"; 502', 502") radially movable within a respective seat (101; 201; 301; 401; 501), and at least one resilient member (103a, 103b; 203; 303a', 303b', 303a", 303b"; 403', 403"; 503', 503") opposing the radial movement of said at least one dampening member (102; 202a, 202b; 302', 302"; 402a', 402b', 402a", 402b"; 502', 502") so as to ensure the contact between each tip (24; 124; 224; 324; 424; 524) and the internal wall (42) of the pumping chamber (44).

2. The vane as claimed in claim 1, wherein it comprises a single damper (100; 200) mounted in a radial seat (101; 201) formed in an axially central region of the vane (120; 220).

3. The vane as claimed in claim 1, wherein it comprises a pair of dampers (300', 300"; 400', 400"; 500', 500") mounted in respective radial seats (301; 401; 501) formed on axially opposite edges of the vane (320; 420; 520).

4. The vane as claimed in any one of preceding claim, wherein the damper (100) or each damper (300', 300") includes a single dampening member (102; 302', 302") and a pair of substantially identical opposing resilient members (103a, 103b; 303a', 303b', 303a", 303b"), arranged to engage one end of the dampening member (102; 302', 302") on the one side and an end wall of the seat (101; 301) on the other side in order to keep the dampening member (102; 302', 302"), in rest conditions, at a substantially central position in said seat (101; 301).

5. The vane as claimed in any one of claims 1 to 3, wherein the damper (200) or each damper (400', 400") includes a pair of dampening members (202a, 202b; 402a', 402b', 402a", 402b") mounted at opposite ends of said seat (201; 401), and a single opposing resilient member (203; 403', 403") located between the dampening members (202a, 202b; 402a', 402b', 402a", 402b") of said pair and arranged to push such members (202a, 202b; 402a', 402b', 402a", 402b"), in rest conditions, against end walls of the respective seats.

6. The vane as claimed in any one of claims 1 to 3, wherein the damper or each damper includes a single dampening member located at a radially inner end of said seat and a single opposing resilient member located at a radially outer end of said seat.

7. The vane as claimed in claim 3, wherein each damper (500', 500") includes a single dampening member (502', 502") and a single opposing resilient member (503', 503") consisting of a leaf spring of which the ends engage the ends of said dampening member (502', 502") and the end walls of the seat (501).

8. The vane as claimed in any one of preceding claim, wherein said dampening member (102) has a mass, or said dampening members (202a, 202b; 302', 302"; 402a', 402b', 402a", 402b"; 502', 502") have an overall mass, smaller than the vane mass.

9. A positive displacement rotary pump having a rotor including at least one vane, characterised in that the at least one vane (120; 220; 320; 420; 520) is a vane as claimed in any one of preceding claim.

10. A method of pumping by means of a positive displacement rotary pump having at least one pumping chamber (44) with an internal wall (42) and a rotor including at least one vane (120; 220; 320; 420; 520) with two tips (124; 224; 324; 424; 524), said vane being arranged to radially slide relative to the rotor (30), during rotation thereof, so that each said tip (124; 224; 324; 424; 524) is in contact with the internal wall (42) of the pumping chamber (44), the rotor and the at least one vane dividing said chamber into at least one intake room (45) and at least one pressure room (46), the method being characterised in that it comprises the step of inertially dampening the at least one vane (120; 220; 320; 420; 520), at points where the radial sliding direction is reversed, so as to ensure the contact, at said points, between each tip of said vane (120; 220; 320; 420; 520) and said internal wall (42) of said at least one chamber (44)), said inertial dampening being achieved by arranging, inside the at least one vane (120; 220; 320; 420; 520), at least one inertial dampening member (102; 202a, 202b; 302', 302"; 402a', 402b', 402a", 402b"; 502', 502") radially movable within a respective seat (101; 201; 301; 401; 501) and associated with opposing resilient members (103a, 103b; 203; 303a', 303b', 303a", 303b"; 403', 403"; 503', 503") arranged to keep the dampening member, in rest conditions, in position in its seat.

11. The method as claimed in claim 10, wherein the inertial dampening is achieved by means of at least one dampening member having a mass, or an overall mass, smaller than the vane mass.

Drawing