CN106168210B

CN106168210B - Displacement pump

Info

Publication number: CN106168210B
Application number: CN201610336904.0A
Authority: CN
Inventors: 马克·圭德蒂; 亚历山大·潘诺
Original assignee: Casappa SpA
Current assignee: Casappa SpA
Priority date: 2015-05-20
Filing date: 2016-05-20
Publication date: 2020-07-14
Anticipated expiration: 2036-05-20
Also published as: EP3096016B1; CN106168210A; EP3096016A1

Abstract

A positive displacement pump, comprising: i) a drive shaft (2); ii) a traction shaft (3) which draws the drive shaft (2) in rotation, the traction shaft (3) being coaxial with the drive shaft (2), a housing seat (6) coming from between the traction shaft (3) and the drive shaft (2) comprising one end of the other, inside the housing seat (6), the traction shaft (3) and the drive shaft (2) comprising in combination a coupling able to transmit any radial load from the traction shaft (3) to the drive shaft (2); iii) a stationary support structure (4) of the drive shaft (2), comprising: -a support (40), relative to which support (40) the drive shaft (2) is rotatable; -a neutralization device, in which the radial load carried on the traction shaft (3) is neutralized and substantially coincides with one or more slide bearings radially sandwiched between the drive shaft (2) and a support (40); the one or more plain bearings comprise at least one first plain bearing (41); iv) at least one first thrust bearing (71) directly or indirectly axially abutting the first portion (33) of the traction shaft (3) for neutralizing axial loads carried on the traction shaft (3).

Description

Displacement pump

Technical Field

The invention relates to a displacement pump, in particular to a gear pump. Gear pumps are meant to transfer energy into a fluid using volume changes induced by the engagement of two rolling bodies.

Background

Known gear pumps comprise:

-two cogwheels, which engage each other;

-a drive shaft driving one of the prospective cogwheels;

-a traction shaft that pulls the drive shaft, the traction shaft extending partially inside the housing of the pump and extending outside the housing, thereby receiving drive torque. In this technical field, the traction shaft is also referred to as support or hub.

Inside the pump housing, the traction shaft is supported by roller bearings (e.g. double row ball bearings) which are used to neutralize axial and radial stresses, preventing them from being transmitted to the drive shaft.

The drawbacks of this constructive solution are the cost of this type of bearing, as well as its size. In fact, the cost and size of these components reflects the cost and overall size of the pump.

US6244842 and US2801593 disclose known pumps.

Disclosure of Invention

In this context, the technical task underlying the present invention is to provide a pump that allows minimizing costs and overall dimensions, while allowing a totally reliable operation.

The technical task and the specific objects stated are substantially achieved by a gear pump comprising the technical features disclosed in one or more of the claims.

Drawings

A better understanding of the further features and advantages of the present invention will be facilitated by a rough, non-limiting description of a preferred, but not exclusive, embodiment of a gear pump according to the present invention, with reference to the accompanying drawings, in which:

figure 1 shows a schematic view of a pump that can incorporate the invention;

figures 2 and 3 show two orthogonal cross-sections of a portion of the pump of the invention;

figures 4 and 5 show two orthogonal cross-sections of a portion of a pump according to an alternative embodiment of the invention.

Detailed Description

In the figures, reference numeral 1 denotes a displacement pump, in particular a gear pump. This gear interacts with the fluid delivered by the pump, determining the energy increase.

As previously indicated, a gear pump means a pump that uses the volume change induced by the meshing of two rolling bodies (usually cogged wheels) to determine the energy transfer to the fluid.

In an alternative embodiment, the pump may be, for example, a pump with pistons sliding in corresponding seats, and wherein said pistons and their seats are drawn in rotation by a swash plate (generally, pumps of this type are known in the art and therefore not further detailed).

The pump 1 includes:

-a drive shaft 2;

a traction shaft 3 which draws the drive shaft 2 in rotation.

In a preferred embodiment, the pump 1 is a gear pump and advantageously the drive shaft 2 is fixedly constrained to at least one of said gears, which determines the increase in fluid energy (said gears coinciding with a rolling body in direct contact with the fluid; conveniently at least one of the drive shaft 2 and said rolling body is a single integrally formed body; advantageously the rolling body is a cogged wheel).

The traction shaft 3 is operatively connected to the drive shaft 2 and transmits radial loads to said drive shaft 2, while being constrained to means for neutralizing the axial loads thereof.

The traction shaft 3 is placed directly or indirectly, through a transmission element, between an engine (typically of the internal combustion type) for driving the pump 1 and the drive shaft 2.

The pump 1 comprises an outer housing 7. The outer housing 7 is part of the protective cover of the pump. Advantageously, the outer casing 7 is obtained by casting.

In the particular embodiment shown by way of example, the drive shaft 2 is located inside a housing 7 of the pump 1. The traction shaft 3 protrudes outside the housing 7 so as to be directly or indirectly connected to the engine. In particular, a portion of the traction shaft 3 external to the casing 7 defines a power take-off operatively connected to said engine.

The housing 7 comprises a mouth 73 for drawing the shaft 3 through the housing 7.

The pump 1 further comprises a stationary support structure 4 for the drive shaft 2.

The support structure 4 comprises:

a support 40, relative to which support 40 said drive shaft 2 is rotatable; advantageously, this support 40 is in a single body with the aforementioned housing 7.

A neutralization device for neutralizing the radial loads carried on the traction shaft 3 (and transmitted to the drive shaft 2 since the shaft 3 does not comprise bearings to withstand said radial loads), the neutralization device being intended to neutralize the radial loads arriving on the drive shaft 2 and originating from elements situated upstream thereof (for example, due to the transmission of motion through a bevel gear pair or a universal joint); the neutralizing means substantially comprise/coincide one or more sliding bearings (without rolling elements) radially sandwiched between said drive shaft 2 and said support 40 (which supports the drive shaft 2); the one or more plain bearings comprise at least one first plain bearing 41. The sliding surface of the first sliding bearing 41 is a cylindrical surface that encloses the rotation shaft of the drive shaft 2. The first sliding bearing 41 is of a commercial type and may comprise steel and polytetrafluoroethylene. The first slide bearing 41 is lubricated.

The first bearing 41 is advantageously a single cylindrical body.

The first bearing 41 is stationary. The drive shaft 2 rotates inside the first bearing 41. The first bearing 41 is in contact with the drive shaft 2 (possibly with an intermediate layer of lubricant) and the support 40. However, the first bearing 41 is not in contact with the traction shaft 3.

The radial thickness of the first bearing 41 is comprised between 0.5 and 3 mm. Conveniently, the ratio between the axial length and the outer diameter of the first bearing 41 is comprised between 0.5 and 15.

The pump 1 further comprises at least one thrust bearing 71, the at least one thrust bearing 71 directly or indirectly axially abutting the first portion 33 of the traction shaft 3 for neutralizing axial loads carried on the traction shaft 3.

For example, in the case of fig. 2, the thrust bearing 71 directly abuts the first portion of the traction shaft 3. In the case of fig. 4, as better explained below, this thrust bearing 71 abuts said first portion 33 by interposing elements referenced 31 and 711.

In particular, the pump 1 comprises a pair of thrust bearings 71, between which the first portion 33 of the traction shaft 3, or the element constrained and fixedly connected to the first portion 33, is axially sandwiched, in order to neutralize the axial loads carried on the traction shaft 3. In this way, axial loads originating from the traction shaft 3 will not be transmitted to the drive shaft 2. The pair of thrust bearings 71 are a pair of axial sliding bearings (hence, no rolling elements).

The first portion 33 of the traction shaft 3 comprises a portion 34 that protrudes radially and extends circumferentially around the axis of rotation of the traction shaft 3.

The pair of thrust bearings 71 is integrally formed with the support structure 4 or fixedly constrained to the support structure 4. The pair of thrust bearings 71 is stationary.

In the preferred embodiment, the pair of thrust bearings 71 includes a pair of slip rings 710. The slip rings 710 are advantageously placed side by side and preferably parallel at a predetermined distance. In particular, the ring 710 extends perpendicularly to the rotation axis of the traction shaft 3. Conveniently, the rings 710 are spaced from each other by a distance of less than 10 mm.

Conveniently, the pair of thrust bearings 71 is interposed between the first slide bearing 41 and the mouth 73, the mouth 73 passing through said housing 7. Conveniently, each of said thrust bearings 71 has an axial thickness comprised between 0.5 and 3 mm.

The minimum distance between the thrust bearing 71 and the mouth 73 through the housing is comprised between 20 and 50 mm.

The minimum distance between the first bearing 41 and the mouth 73 through the housing is comprised between 25 and 70 mm.

As illustrated in the drawings, the traction shaft 3 is not supported by roller bearings. Advantageously, the drive shaft 2 is also not supported by roller bearings.

The traction shaft 3 and the drive shaft 2 are coaxial, one of them comprising a seat 6, said seat 6 being intended to receive the end of the other. Conveniently, the traction shaft 3 and the drive shaft 2 are mutually engaged inside the housing seat 6.

Inside the containment seat, the traction shaft 3 and the drive shaft 2 comprise, in combination, a coupling able to transmit any radial load from the traction shaft 3 to the drive shaft 2.

The coupling, which enables any radial load to be transmitted from the traction shaft 3 to the drive shaft 2, comprises transverse portions of the traction shaft 3 and of the drive shaft 2, which are complementary in shape and cooperate with each other. The transverse portion is thus able to correct the centre of the

shafts

2 and 3.

Inside this housing seat 6, said traction shaft 3 and said drive shaft 2 comprise, in combination, a toothed transmission device for transmitting a driving torque from the traction shaft 3 to said drive shaft 2.

The toothed means act on the shaft 2 and the first part 9 of the shaft 3.

A complementary shaped portion for transmitting radial loads acts on the second portion 90 of the shafts 2 and 3 (as previously mentioned, the second portion 90 of the

shafts

2 and 3 also enables centring of the two shafts). Typically, the first portions 9 of the

shafts

2 and 3 and the second portions 90 of the

shafts

2 and 3 defined above are adjacent.

In a preferred embodiment, the housing seat 6 is moulded into the traction shaft 3. Therefore, the drive shaft 2 protrudes inside the traction shaft 3. In a preferred embodiment, the drive shaft 2 has a first plurality of teeth 21, which first plurality of teeth 21 meshes with a second plurality of teeth 35 belonging to said traction shaft 3. Conveniently, the first plurality of teeth 21 project radially from the base of the rotation axis remote from said traction shaft 3, while the second plurality of teeth 35 project radially from the base of the rotation axis towards said traction shaft 3.

The first plain bearing 41 comprises a lubricating bushing 410, the lubricating bushing 410 being fixedly constrained to said supporting structure 4 and said drive shaft 2 rotating in said bushing 410.

Inside the housing 7, a lubrication chamber 70 communicates with the first slide bearing 41 and the pair of thrust bearings 71. The pump 1 further comprises a conduit for feeding lubricant to the lubrication chamber 70.

This enables lubrication of the thrust bearings 71 facing each other in the lubrication chamber 70.

Conveniently, the pump 1 comprises an oil seal 72, the oil seal 72 helping to delimit said lubrication chamber 71. The oil seal 72 extends radially between the traction shaft 3 and a part of said housing 7.

In the embodiment of fig. 2 and 3, the traction shaft 3 comprises a shoulder 30, the shoulder 30 being interposed between the pair of thrust bearings 71 and being mounted between the pair of thrust bearings 71. The shoulder 30 is made in a single, integrally formed body with the other components of the traction shaft 3.

In the embodiment of fig. 4 and 5, the traction shaft 3 comprises a circumferential seat 31, the circumferential seat 31 lying in a plane transversal (preferably, perpendicular) to the rotation axis of said traction shaft 3; the portion of the west ring 32 integral with the traction 3 is located in said seat 31 and projects radially from the seat 31, contacting at least one thrust bearing 71 via at least one first ring 711, the first ring 711 being interposed between said west ring 32 and said thrust bearing 71.

The invention also relates to a method for operating a volumetric pump, in particular a gear interacting with a fluid conveyed by the pump in order to determine an increase in its energy. The pump 1 has one or more of the features described above. The pump 1 comprises a drive shaft 2 and a traction shaft 3, said traction shaft 3 drawing said drive shaft 2 in rotation. Advantageously, the drive shaft 2 may be fixedly constrained to at least one of said gears. The method comprises the following steps:

the axial load present on the traction shaft 3 is neutralized by at least one thrust bearing 71, the thrust bearing 71 axially abutting directly or indirectly, through at least one intermediate element, the first portion 33 of the traction shaft 3;

-transferring radial loads carried on the traction shaft 3 to the drive shaft 2;

the radial load of the drive shaft 2 is neutralized by one or more slide bearings which enclose and support said drive shaft 2.

Thus, the invention as conceived is able to obtain a plurality of advantages.

In particular, the overall size of the pump on the present invention is reduced.

The use of sliding bearings instead of roller bearings is more compact (especially in the axial direction of the traction shaft 3) and cost-effective. In particular, the drive shaft 2 is supported by radial sliding bearings which are used not only to neutralize the radial loads generated by the shaft 2, but also to neutralize the radial loads originating from the shaft 3. The axial loads carried on the shaft 3 are neutralized by the pairs of thrust bearings and are thus transmitted to the shaft 2.

Therefore, without departing from the concept of the invention, several variations and modifications can be made, which are within the scope of the invention. Moreover, all the details of the invention may be substituted by technically equivalent elements. In practice, all the materials used, as well as the dimensions, may be of any type according to requirements.

Claims

1. A positive displacement pump, comprising:

i) a drive shaft (2);

ii) a traction shaft (3) which draws the drive shaft (2) in rotation, the traction shaft (3) being coaxial with the drive shaft (2), a housing seat (6) coming from between the traction shaft (3) and the drive shaft (2) comprising one end of the other, inside which housing seat (6) the traction shaft (3) and the drive shaft (2) comprise in combination a coupling;

iii) a stationary support structure (4) of the drive shaft (2), comprising:

-a support (40), relative to which support (40) the drive shaft (2) is rotatable;

-a neutralization device, in which the radial load carried on the traction shaft (3) is neutralized and substantially coincides with one or more plain bearings without rolling elements, radially sandwiched between the drive shaft (2) and a support (40); the one or more plain bearings comprise at least one first plain bearing (41);

iv) at least one thrust bearing (71) directly or indirectly axially abutting the first portion (33) of the traction shaft (3) for neutralizing axial loads carried on the traction shaft (3);

characterized in that, since the traction shaft (3) does not comprise bearings to withstand the radial loads, the coupling is able to transmit any radial load from the traction shaft (3) to the drive shaft (2);

the coupling capable of transmitting any radial load from the traction shaft (3) to the drive shaft (2) comprises lateral portions of the traction shaft (3) and the drive shaft (2) that are complementary in shape and that fit each other;

-inside the housing seat (6), the traction shaft (3) and the drive shaft (2) comprise, in combination, a geared transmission device that transmits the driving torque from the traction shaft (3) to the drive shaft (2), acting on the drive shaft (2) and on a first portion (9) of the traction shaft (3), in addition to the coupling able to transmit any radial load from the traction shaft (3) to the drive shaft (2);

the complementary shaped portions for transmitting radial loads act on the second portions (90) of the drive shaft (2) and of the traction shaft (3), the second portions (90) of the drive shaft (2) and of the traction shaft (3) being able to center the drive shaft (2) and of the traction shaft (3).

2. The pump of claim 1, wherein the pump is a gear pump and comprises at least one pair of cogged wheels that interact with the fluid to determine an increase in energy of the fluid; the drive shaft (2) is fixedly constrained to at least one of the cogwheels.

3. The pump according to claim 1, characterized in that the first plain bearing (41) comprises a lubricating sleeve (410), the lubricating sleeve (410) being fixedly constrained to the stationary support structure (4) and the drive shaft (2) rotating within the lubricating sleeve (410).

4. Pump according to claim 1, characterized in that it comprises an outer casing (7), the traction shaft (3) projecting outside the outer casing (7) so as to be able to be connected directly or indirectly to an engine.

5. Pump according to claim 4, characterized in that inside the outer casing (7) there is a lubrication chamber (70), the lubrication chamber (70) communicating with the first plain bearing (41) and with the thrust bearing (71).

6. A pump according to claim 1, characterized in that the at least one thrust bearing (71) comprises a pair of thrust bearings, the first portion (33) of the traction shaft (3) comprising a shoulder (30), the shoulder (30) abutting the pair of thrust bearings (71) and being mounted between the pair of thrust bearings (71).

7. Pump according to claim 1, characterized in that the traction shaft (3) comprises a circumferential seat (31), the circumferential seat (31) lying in a plane tangential to the rotation axis of the traction shaft (3), and in that the pump (1) comprises a sigma ring (32), the sigma ring (32):

-at least partially in said circumferential seat (31);

-contacting said thrust bearing (71) by means of at least one first ring (711), which first ring (711) is interposed between said siege ring (32) and said thrust bearing (71).

8. Pump according to any of the preceding claims, characterized in that the traction shaft (3) and the drive shaft (2) are not supported by roller bearings.