EP3096016B1

EP3096016B1 - Volumetric pump

Info

Publication number: EP3096016B1
Application number: EP16169752.9A
Authority: EP
Inventors: Alessandro PANNO; Marco Guidetti
Original assignee: Casappa SpA
Current assignee: Casappa SpA
Priority date: 2015-05-20
Filing date: 2016-05-16
Publication date: 2021-04-07
Anticipated expiration: 2036-05-16
Also published as: CN106168210B; CN106168210A; EP3096016A1

Description

The present invention relates to a volumetric pump, in particular a gear pump. Gear pump means a pump in which the change in volume induced by the meshing of two rolling bodies is exploited to transfer energy to a fluid.
There are known gear pumps comprising:

two cogwheels which engage with each other;
a drive shaft which drives one of said due cogwheels;
a shaft drawing the drive shaft; the drawing shaft extends in part inside a casing of the pump and extends outside said casing so as to receive the drive torque. In the technical field the drawing shaft is also known as a support or hub.

Inside the pump casing, the drawing shaft is supported by roller bearings, for example double row ball bearings, which serve to neutralise both axial stresses and radial stresses, preventing them from being transferred onto the drive shaft.
A drawback of this constructive solution is tied to the cost of this type of bearings, as well as their dimensions. In fact, the cost and dimensions of these components are reflected in the cost and overall dimensions of the pump.
Known pumps are disclosed by US6244842 , US2801593 and US2412588 . In this context, the technical task at the basis of the present invention is to provide a pump which enables costs and overall dimensions to be minimised while permitting wholly reliable operation.
The stated technical task and specified objects are substantially achieved by a gear pump comprising the technical features disclosed in one or more of the appended claims.
Additional features and advantages of the present invention will become more apparent from the approximate, and thus non-limiting description, of a preferred, but not exclusive embodiment of a gear pump, as illustrated in the appended drawings, in which:

figure 1 shows a schematic view of a pump which can incorporate the present invention;
figures 2 and 3 show two orthogonal and sectional views of a portion of a pump according to the present invention;
figures 4 and 5 show two orthogonal and sectional views of a portion of a pump according to an alternative embodiment of the present invention.

In the appended figures, the reference number 1 indicates a volumetric pump, in particular a gear pump. The gears interact with a fluid transiting through the pump, determining an increase in energy.
As previously indicated, gear pump means a pump in which the change in volume induced by the meshing of two rolling bodies (typically cogwheels) is exploited to determine a transfer of energy to the fluid.
In an alternative embodiment, the pump could be, for example, a pump with pistons sliding in corresponding seatings, and in which the pistons and the seatings thereof are drawn in rotation by an inclined plate (in general terms pumps of this type are well known in the art and will therefore not be further detailed).
The pump 1 comprises:

a drive shaft 2;
a drawing shaft 3 which draws in rotation the drive shaft 2.

In the preferred embodiment, the pump 1 is a gear pump and the drive shaft 2 is advantageously solidly constrained to at least one of the gears which determine an increase in energy of the fluid (said gears coincide with rolling bodies placed in direct contact with the fluid; conveniently, the drive shaft 2 and at least one of said rolling bodies are in a single monolithic body; advantageously, the rolling bodies are cogwheels).
The drawing shaft 3 is operatively linked to the drive shaft 2 and transfers its radial loads to the latter, whilst being constrained to means for neutralising its axial loads.
The drawing shaft 3 is placed, directly or indirectly by means of a transmission member, between a motor (typically of the internal combustion type) for driving the pump 1 and the drive shaft 2.
The pump 1 comprises an external casing 7. The external casing 7 is part of the protective enclosure of the pump. Advantageously, the external casing 7 is obtained by casting.
In the specific embodiment illustrated by way of example, the drive shaft 2 lies internally of the casing 7 of the pump 1. The drawing shaft 3 projects externally of the casing 7 in order to enable a direct or indirect connection with a motor. In particular, a part of the drawing shaft 3 outside the casing 7 defines a power take-off operatively connected to the motor.
The casing 7 comprises a mouth 73 for the drawing shaft 3 to pass through the casing 7.
The pump 1 also comprises a static support structure 4 for the drive shaft 2.
The support structure 4 comprises:

a support 40 with respect to which the drive shaft 2 can rotate; advantageously the support 40 is in a single body with the aforesaid casing 7;
means for neutralising the radial loads bearing on the drawing shaft 3 (and which are transferred to said drive shaft 2, since the shaft 3 does not comprise bearings to oppose said radial loads); the neutralising means thus serve to neutralise the radial loads that arrive on the drive shaft 2 and originate from elements located upstream thereof, for example because of a transmission of motion through a bevel gear pair or universal joint; the neutralising means substantially comprise/coincide with one or more sliding bearings (devoid of rolling elements) radially interposed between the drive shaft 2 and the support 40 (it/they supports/support the drive shaft 2); said one or more sliding bearings comprising at least a first sliding bearing 41. The sliding surface of the first sliding bearing 41 is a cylindrical surface that envelops the rotation axis of the drive shaft 2. The first sliding bearing 41 is of a commercial type and can comprise steel and Teflon. It is lubricated.

The first bearing 41 is advantageously a single cylindrical body.
The first bearing 41 is static. The drive shaft 2 rotates inside the first bearing 41. The first bearing 41 is in contact with the drive shaft 2 (possibly through an interposed layer of lubricant) and the support 40. The first bearing 41 is not, however, in contact with the drawing shaft 3.
The radial thickness of the first bearing 41 is comprised between 0.5 and 3 millimetres. Conveniently, the ratio between the axial extent and outer diameter of the first bearing 41 is comprised between 0.5 and 1.5.
The pump 1 also comprises at least a thrust bearing 71 which axially abuts, directly or indirectly, a first portion 33 of the drawing shaft 3 in order to neutralise axial loads bearing on the drawing shaft 3.
For example, in the case of figure 2, the thrust bearing 71 directly abuts a first portion of the drawing shaft 3. In the case of figure 4, as better explained below, the thrust bearing 71 abuts the first portion 33 by interposition of the elements indicated by the reference numbers 31 and 711.
In particular, the pump 1 comprises a pair of thrust bearings 71, axially interposed between which is the first portion 33 of the drawing shaft 3 or an element constrained and/or solidly joined thereto in order to neutralise axial loads bearing on the drawing shaft 3. In this manner, the axial loads originating from the drawing shaft 3 will not be transferred onto the driven shaft 2. The pair of thrust bearings 71 is a pair of axial sliding bearings (thus devoid of rolling elements).
The first portion 33 of the drawing shaft 3 comprises a portion 34 which projects radially and extends circumferentially about the rotation axis of the drawing shaft 3.
The pair of thrust bearings 71 is integral with or solidly constrained to said support structure 4. They are static.
In the preferred embodiment, the pair of thrust bearings 71 comprises a pair of sliding rings 710. The sliding rings 710 are advantageously positioned side by side at a predetermined distance and preferably parallel. In particular, said rings 710 extend perpendicularly to a rotation axis of the drawing shaft 3. Conveniently, they are spaced at a distance of less than 10 millimetres from each other.
Conveniently, the pair of thrust bearings 71 is interposed between the first sliding bearing 41 and the mouth 73 passing through the casing 7.
Conveniently, the axial thickness of each of said thrust bearings 71 is comprised between 0.5 and 3 millimetres.
The minimum distance between the thrust bearing 71 and the mouth 73 passing through the casing is comprised between 20 and 50 millimetres.
The minimum distance between the first bearing 41 and the mouth 73 passing through the casing 7 is comprised between 25 and 70 millimetres.
As exemplified in the appended figures, the drawing shaft 3 is not supported by roller bearings. Conveniently, nor is the drive shaft 2 supported by roller bearings.
The drawing shaft 3 and drive shaft 2 are coaxial, one of the two comprising a seating 6 for housing an end of the other. Conveniently, the drawing shaft 3 and the drive shaft 2 reciprocally mesh internally of the housing seating 6.
Internally of the housing seating, the drawing shaft 3 and the drive shaft 2 comprise in combination a coupling which enables any radial loads to be transferred from the drawing shaft 3 to the drive shaft 2.
The coupling which enables any radial loads to be transferred from the drawing shaft 3 to the drive shaft 2 comprises transversal sections of the drawing shaft 3 and the drive shaft 2, which are complementarily shaped and fitted into one another. They thus enable correct centring of the shafts 2 and 3.
Internally of the housing seating 6, said drawing shaft 3 and said drive shaft 2 comprise in combination cogged transmission means for transmitting the drive torque from the drawing shaft 3 to the drive shaft 2.
The cogged means act on a first portion 9 of the shaft 2 and of the shaft 3. The complementarily shaped sections for the transmission of radial loads act on a second portion 90 of the shaft 2 and the shaft 3 (as previously mentioned, the second portion 90 also enables centring of the two shafts). Typically, the first and second shafts 9, 90 defined above are adjacent.
In the preferred embodiment the housing seat 6 is fashioned in said drawing shaft 3. The drive shaft 2 thus projects inside the drawing shaft 3. In the preferred embodiment, the drive shaft 2 has a first plurality 21 of teeth that mesh with a second plurality 35 of teeth belonging to said drawing shaft 3. Conveniently, the first plurality 21 of teeth project radially from a base away from the rotation axis of the drawing shaft 3, whilst the second plurality 35 of teeth project radially from a base toward the rotation axis of the drawing shaft 3.
The first sliding bearing 41 comprises a lubricated bushing 410 solidly constrained to said support structure 4 and in which said drive shaft 2 rotates.
Inside the casing 7 there is a lubricating chamber 70 in communication with said first sliding bearing 41 and said pair of thrust bearings 71. The pump 1 further comprises a conduit for feeding lubricant to said lubricating chamber 70.
This makes it possible to lubricate the thrust bearings 71 which are facing each other in the lubricating chamber 70.
Conveniently, the pump 1 comprises an oil seal 72 which contributes to delimiting said lubricating chamber 71. The oil seal 72 extends radially between the drawing shaft 3 and a part of the casing 7.
In the embodiment of figures 2 and 3, the drawing shaft 3 comprises a shoulder 30 which is interposed between said pair of thrust bearings 71 and is fitted between them. The shoulder 30 is made in a single monolithic body with other parts of the drawing shaft 3.
In the embodiment of figures 4 and 5, the drawing shaft 3 comprises a circumferential seating 31 which lies in a plane transversal (preferably perpendicular) to the rotation axis of the drawing shaft 3; a seeger ring 32 integral with the drawing shaft 3 is positioned in part in said seating 31 and comes out of it radially, encountering at least a thrust bearing 71 via at least a first ring 711 interposed between said seeger ring 32 and said thrust bearing 71.
The present invention also relates to a functioning method of a volumetric pump, in particular with gears interacting with a fluid transiting through the pump in order to determine an increase in energy thereof. The pump 1 has one or more of the features described previously. The pump 1 comprises a drive shaft 2 and a shaft 3 drawing in rotation said drive shaft 2. Advantageously, the drive shaft 2 could be solidly constrained to at least one of the gears. The method comprises the steps of:

neutralising the axial loads present on the drawing shaft 3 by means of at least a thrust bearing 71 which axially abuts a first portion 33 of the drawing shaft 3 directly or indirectly by means of at least an interposed element;
transmitting to the drive shaft 2 the radial loads bearing on the drawing shaft 3;
neutralising the radial loads of the drive shaft 2 by means of one or more sliding bearings which envelop and support said drive shaft 2.

The invention thus conceived enables multiple advantages to be obtained. In particular, it permits a reduction in the overall dimensions of the pump. In fact, the use of sliding bearings rather than roller bearings enables greater compactness (especially in the axial direction of the drawing shaft 3) and cost savings. In particular, the drive shaft 2 is supported by radial sliding bearings that are used not only to neutralise the radial loads generated by the shaft 2, but also to neutralise the radial loads originating from the shaft 3. The axial loads bearing on the shaft 3 are neutralised by a pair of thrust bearings and are thus not transferred to the shaft 2.
The invention thus conceived is susceptible of numerous modifications and variants, all falling within the scope of the inventive concept characterising it. Moreover, all of the details may be replaced with technically equivalent elements. In practice, all of the materials used, as well as the dimensions, may be of any type, according to need.

Claims

A volumetric pump comprising:
i) a drive shaft (2);

ii) a shaft (3) drawing in rotation said drive shaft (2), said drawing shaft (3) being coaxial with the drive shaft (2); one from between the drawing shaft (3) and the drive shaft (2) comprising a housing seating (6) of an end of the other; internally of the housing seating (6), the drawing shaft (3) and the drive shaft (2), comprising in combination a coupling;

iii) a static support structure (4) of the drive shaft (2) comprising:
- a support (40) with respect to which the drive shaft (2) can rotate;

- neutralising means of the radial loads bearing on the drawing shaft (3) and coinciding substantially with one or more sliding bearings devoid of rolling elements radially interposed between the drive shaft (2) and the support (40); said one or more sliding bearings comprising at least a first sliding bearing (41);

iv) at least one thrust bearing (71) which axially abuts, directly or indirectly, a first portion (33) of the drawing shaft (3) in order to neutralise axial loads bearing on the drawing shaft (3);
characterised in that said coupling enables transferring any radial loads from the drawing shaft (3) to the drive shaft (2), since the drawing shaft (3) does not comprise bearings to oppose said radial loads;
said coupling enabling transfer of any radial loads from the drawing shaft (3) to the drive shaft (2) comprises transversal sections of the drawing shaft (3) and the drive shaft (2) which sections are complementarily shaped and fitted one in another;
said drawing shaft (3) and said drive shaft (2), internally of the housing seating (6), in addition to said coupling enabling transfer of any radial loads from the drawing shaft (3) to the drive shaft (2), comprise in combination cogged transmission means of the drive torque from the drawing shaft (3) to the drive shaft (2); the cogged transmission means act on a first part (9) of the drive shaft (2) and of the drawing shaft (3);
the complementarily shaped sections for the transmission of radial loads act on a second part (90) of the drive shaft (2) and the drawing shaft (3), the second part (90) of the drive shaft (2) and the drawing shaft (3) enabling centring of the drive shaft (2) and of the drawing shaft (3).
The pump according to claim 1, characterised in that said pump is a gear pump and comprises at least a pair of cogwheels which interact with the fluid determining an increase in energy thereof; said drive shaft (2) being solidly constrained to at least one of said cogwheels.
The pump according to claim 1 or 2, characterised in that said first sliding bearing (41) comprises a lubricated bushing (410) solidly constrained to said static support structure (4) and in which said drive shaft (2) rotates.
The pump according to any one of the preceding claims, characterised in that it comprises an external casing (7), said drawing shaft (3) projecting externally of said external casing (7) in order to enable a direct or indirect connection with a motor.
The pump according to claim 4, characterised in that a lubricating chamber (70) is present internally of the external casing (7), which lubricating chamber (70) is in communication with said first sliding bearing (41) and with said thrust bearing (71).
The pump according to any one of the preceding claims, characterised in that said at least one thrust bearing (71) comprises a pair of thrust bearings, said first portion (33) of the drawing shaft (3) comprises a shoulder (30) which abuts said pair of thrust bearings (71) and which is fitted between them (71).
The pump according to any one of claims from 1 to 6, characterised in that said drawing shaft (3) comprises a circumferential seating (31) which lies in a plane transversal to the rotation axis of the drawing shaft (3), the pump (1) comprising a seeger ring (32) which:
- is positioned at least in part in said seating (31);

- abuts said thrust bearing (71) by at least a first ring (711) interposed between said seeger ring (32) and said thrust bearing (71).
The pump according to any one of the preceding claims, characterised in that said drawing shaft (3) and said drive shaft (2) are not supported by roller bearings.